Fill material compensator for an automatic hydro-mechanical land leveler

ABSTRACT

Control apparatus including an action booster than can be attached to typical land levelers of the type having an elongated center articulated frame suitably supported at its ends and provided intermediate its ends with a scraper blade fixedly attached thereto and further supported adjacent the center thereof by automatic hydro-mechanical controlled wheels to maintain the height of the blade at a preset relationship with respect to a straight line extending between the support structure adjacent the ends thereof to effect land leveling as it is caused to travel over the surface of the earth. The apparatus boosts the response of the drive structure for the intermediate or blade support wheels to the elevation of the irregularities resulting in an optimum refinement of the leveling action thereof which is controlled by the relationship of the compacted ground contact point of the blade support wheels and a line between the compacted ground contact points of the front and rear support structure. The responsive action compensates for loose material in fill areas and for the problem that fill material would not heretofore spill under the blade properly to fill low places to the exact height of the blade.

United States Patent 1191 Servatius 1 Apr. 3, 1973 [54] FILL MATERIALCOMPENSATOR FOR AN AUTOMATIC HYDRO- MECHANICAL LAND LEVELER [76]Inventor: John B.- Servatius, PO. Box 26, East Prairie, Mo. 63845 22Filed: 0a. 15, 1971 21 Appl. No.2 189,609

Primary Examiner-Robert E. Pulfrey Assistant Examiner-Stephen C,Pellegrino Attorney-John R. Walker [57] ABSTRACT Control apparatusincluding an action booster than can be attached to typical landlevelers of the type having an elongated center articulated framesuitably supported at its endsand provided intermediate its ends with ascraper blade fixedly attached thereto and further supported adjacentthe center thereof by automatic hydro-mechanical controlled wheels tomaintain the height of the blade at a preset relationship with respectto a straight line extending between the support structure adjacent theends thereof to effect land leveling as it is caused to travel over thesurface of the earth. The apparatus boosts the response of the drivestructure for the intermediate or blade support wheels to the elevationof the irregularities resulting in an optimum refinement of the levelingaction thereof which is controlled by the relationship of the compactedground contact point of the blade support wheels and a line between thecompacted ground contact points of the front and rear support structure.The responsive action compensates for loose material in fill areas andfor the problem that fill material would not heretofore spill under theblade properly to fill low places to the exact height of the blade.

5 Claims, 5 Drawing Figures PATENTEDAPRB I975 3. 724,556 SHEET 1 OF 2FIG. I

FIG. 2

INVENTOR. JOHN B. SERVATIUS p NI PATENTEDAPR 3 I973 SHEET 2 BF 2 @N NN IN VEN TOR. JOHN B. SERVATIUS FILL MATERIAL COMPENSATOR FOR AN AUTOMATICHYDRO-MECHANICAL LAND LEVELER BACKGROUND OF THE INVENTION 1. Field ofthe Invention This invention relates to land levelers.

2. Description of the Prior Art In automatic hydro-mechanical landlevelers of the general type described in Hobday U.S. Pat. No. 2,792,651and Gurries et al. U.S. Pat. No. 3,000,122, the usual practice is tomount a valve assembly on one of the articulating frame members which ismechanically linked to the other frame member so that when theintermediate wheels supporting the portion of the frame having the bladeattached thereto pass over an irregular surface, the articulating motionof the frame members causes the valve to sense the degree ofirregularity and drive the intermediate wheels in a direction whichraises the blade as it passes over a depression and lowers the blade asit passes over a ridge. In other words, the valve is constantly sensingthe irregularity and is constantly trying to maintain a straight linealong the longitudinal axes of the articulating frame members by raisingor lowering the intermediate wheels.

Certain disadvantages or problems prevail in land levelers of theabove-described types, among which are: First, the fill material beingloose when deposited in the low-lying areas will become compacted afternatural settling has occurred, thus allowing a depression to exist eventhough the area appeared to be perfectly level immediately following theland leveling operation. Secondly, the blade or bowl of a finish landleveler moves only a slight distance, the space below the blade edge andthe depression usually is rather narrow. Accordingly, the fill materialwill not readily spill under the blade to fill to the exact height ofthe blade. This problem is particularly prevalent when the moisturecontent of the fill material is high or the fill material is in clumpsrather than being a fine powder or dust.

The former of the above-mentioned problems was recognized by theShumaker U.S. Pat. No. 2,650,441, from which the following is a quote:

It has been found that if a field is leveled by cutting high places to alevel and filling low places to that level, it will not be level afterplowing or tilling.

This is due to the settling of the loose earth in the fills and to theexpansion of the formerly hard packed earth in the scraped off highspots. "Another object of this invention is to provide automatic meansfor raising and lowering a scraper that is substantially rigid about ahorizontal axis and issupported fore and aft by ground-engaging supportstructure. Intermediate the fore and aft support structure are wheelswhich are free to drop into low places or raise when passing over higherplaces and the action of the wheels is used to raise and lower thecutting blade a proportionate distance. Certain problems prevail inpracticing the 441 patent. Among these is the fact that it will notcorrect itself as it passes over an irregular surface. In other words,the operator must constantly evaluate the condition of the soil so thathe can at all times adjust the automatic operation of the blade.Secondly, the features of the 441 patent cannot be incorporated with aland leveling machine having a frame that articulates about a horizontalaxis.

In addition to the above-mentioned patents, the state of the art asknown by the applicant includes the Hobday U.S. Pat. No. 2,846,792;Gurries et al. U.S. Pat. Nos. 2,833,777; 2,893,140; and 2,900,746;Waterson U.S. Pat. Nos. 3,210,871; 3,287,835; 3,353,288; and 3,516,497.Additionally, it includes the Shuey U.S. Pat. No. 2,503,638; White U.S.Pat. No. 2,720,716; Kirchner U.S. Pat. No. 2,732,640; Shumaker et al.U.S. Pat. No. 2,842,874; Knapp et al. U.S. Pat. No. 3,092,922; and Younget al. U.S. Pat. No. 3,428,133. None of the above references show orsuggest applicants device.

SUMMARY OF THE INVENTION The present invention is directed towardsovercoming the disadvantages and problems relative to previous landlevelers. The concept of the present invention is to provide a boosteraction valve control apparatus that can be attached to land levelers ofthe type having an elongated center articulated frame suitably supportedat its ends and provided intermediate its ends with a scraper bladefixedly attached thereto and further supported adjacent the centerthereof by automatic hydromechanical controlled wheels to maintain theheight of the blade at a present relationship with respect to a straightline extending between the support structure adjacent the ends thereofto effect land leveling as it is caused to travel over the surface ofthe earth.

The apparatus boosts the response of the drive structure for theintermediate or blade support wheels to the elevation of theirregularity resulting in an optimum refinement of the leveling actionthereof. This is controlled by the relationship of the compacted groundcontact point of the blade support wheels and a line between thecompacted ground contact points of the front and rear support structure.An important feature of the invention is that the responsive actioncompensates for loose material in fill areas by overfilling the lowerareas. Additionally, the exaggerated movement of the blade in responseto the irregularities assures that the fill material contained withinthe bowl is spilled under the blade. In other words, even when themoisture content of the fill material is high, the compensator of thepresent invention assures that it will be discharged from the bowl asthe blade passes over low places.

Another important feature of the compensator of the present invention isthat it automatically corrects itself, i.e., the action for one possiblesetting can be thought of as the original response equal to themagnitude of the irregularity or a unit of one, plus a percentage of theoriginal unit, e.g., percent, plus this percentage, or 75 percent of theoriginal unit or 0.562, plus this pereentag'e of 75 percent of the 75percent of the 75 percent of the original unit or 0.422, etc., toapproximately 3.7 times the magnitude of the irregularity. The inventionincludes means for adjusting the amount of the booster action desired.

Another important feature of the compensator of the present invention isthat it will not over-react since the hydro-mechanical response is notinstantaneous. Accordingly, the blade support wheels pass immediatelybehind the blade and the leveling action of the blade to theseirregularities is constantly changing the elevation of the compactedground contact point for the blade support wheels, i.e., in relation tothe straight line extending between the compacted ground contact pointsof the front and rear wheels which effects the vertical articulation ofthe land leveler and thus modifies the response. This continual actionand reaction will produce a more accurately leveled field or roadbedthan known prior land levelers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of avertical articulated land plane showing the fill material compensator ofthe present invention installed thereon.

FIG. 2 is a plan view of the vertical articulated land plane of thepresent invention.

FIG. 3 is an enlarged sectional view taken as on the line III-III ofFIG. 2.

FIG. 4 is an enlarged sectional view taken as on the line IV-IV of FIG.1.

FIG. 5 is a side elevational view of a horizontal and verticalarticulated land plane showing a modified embodiment of the fillmaterial compensator of the present invention installed thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The fill material compensatorapparatus 11 of the present invention is adapted to be used with any ofthe vertical automatic hydro-mechanical levelers 13 such as the wellknown articulated type shown in U.S. Pat. No. 3,000,122. The leveler 13is pulled in a direction shown by an arrow 15 by a tractor or the like(not shown) which may be attached to a drawbar 17 in a well knownmanner.

The land leveler 13 includes an articulated frame 19, i.e., a main framemember 21 and a tail frame member 23. The forward end of the main framemember 21 is supported by a pair of wheels 25 and the rearward end ofthe tail frame member 23 is supported by a caster wheel 27. In otherwords, the wheels 25, 27 support the fore and aft ends of thearticulated frame 19 at a fixed distance above the ground.

A pair of movable wheels 29 support the midportion of the articulatedframe 19 at various distances above the ground. This will be more fullydisclosed later in the specification. The leveler 13 includes atransverse cam shaft 31 rotatably attached to the main frame member 21so as to be free to rotate about a first axis and having cranklikemembers 33 fixedly attached thereto for rotatably supporting the pair ofwheels 29 which rotate about a second axis.

The leveler 13 also includes a scraper blade assembly 35 rigidlyattached to the frame member 21 and depending therefrom for scrapingaway higher areas of land and depositing the thusly collected fillmaterial into lower lying areas as the leveler machine 13 is caused totravel over the irregular surface of the earth in a manner previouslydescribed. A hydraulic ram as sembly 38, being operably interposedbetween the cam shaft 31 and the frame member 21, may be suitablyactuated for causing rotation about the first axis of the cam shaft 31,thus raising and lowering the scraper blade assembly 35.

A hydraulic directional control valve 39 is operably interposed betweenthe ram assembly 37 and a source 41 of hydraulic fluid under pressurefor controllably actuating the ram assembly 37. It should be understoodthat the articulated frame 19 pivots about a horizontally disposed pivotpin 43, i.e., the tail frame member 23 is pivotally attached to the mainframe member 21 by the pivot pin 43 in the usual manner.

The fill material compensator 11 of the present invention generallycomprises a bell crank leveler assembly 45 having at least one verticalarm 47 and a horizontal arm 49. The bell crank lever assembly 45 ispivotally attached to the articulating frame 19. More specifically, thebell crank leveler 45 is pivotally attached to the frame member 23 by ahorizontally disposed pivot pin 51 as best viewed in FIGS. 3 and 4 ofthe drawings. Additionally, the apparatus 11 includes first linkagemeans or a linkage assembly 53 interconnecting the vertical arm 47 andthe valve 39 for causing the valve 39 to be initially actuated when theframe 19 articulates as a result of the wheels 29 rolling over a slightmound or depression which causes the ram assembly 37 to rotatably drivethe cam shaft 31 about the first axis thereof to an interim position forreturning the frame 19 to a substantially straight line condition.

Further, the apparatus 11 includes a cam lever 55 suitably attached tothe cam shaft 31 in any well known manner as by welding or the like.Further yet, the apparatus 11 includes a booster linkage assembly 57which interconnects the horizontal arm 49 and the cam lever 55 forcausing the ram assembly 37 to overcompensate for the irregularity ofthe surface and further rotatably-drive the cam shaft 31 about the firstaxis, i.e., beyond the just-mentioned interim position. This causes thescraper blade assembly 35 to slightly un dercut the higher-lying areas,that is, exaggerate the amount of cutting, and slightly overfill thelower-lying areas, resulting in more perfect planed leveling afternatural settling of the fill material has occurred.

Particular attention is now directed towards FIGS. 3 and 4 of thedrawings wherein it may be seen that the vertical arm 47 preferablycomprises an inverted U- shaped structure having the vertical arm 47 anda second vertical arm 59 supported a spaced apart distance therefrom bya horizontal member 61. The vertical arms 47, 59 are provided withaligned apertures 63 for receiving the pivot pin'51. In other words, apair of lugs 65 are fixedly attached to the frame member 23 and areprovided with apertures in alignment with the aperture 63 for alsopivotally receiving the pivot pin 51. The vertical arms 47, 59 areprovided with a'plurality of apertures 67 along the length thereof,e.g., apertures 67a-67i.

The linkage assembly 53 preferably includes an elongated rod 69 havingone end thereof pivotally attached to the valve structure 39 with aclevis pin 71. The opposite end of the rod 69 is provided with athreaded portion for threadedly receiving a sleevelike member It shouldbe understood that the valve 39 includes well known structure obvious tothose skilled in the art, e.g., like that described in the Gur ries etal. U.S. Pat.

No. 2,990,746. In other words, the valve 39 is the same type as thatused on automatic header controls for combines and cotton pickers.Accordingly, the valve 39 includes movable actuating structure as avalve lever or a bell crank member 75 which pivots about a pivot pin 77as the rod 69 is caused to move to and fro substantially along thelongitudinal axis of the leveler 11 in a manner yet to be described.

From FIG. 3 of the drawings, it may be seen that moving the rod 69 tothe right causes additional actuating structure 78 of the valve 39 to bemoved downwardly and conversely, moving the rod 69 to the left allowsthe actuating structure to move upwardly. It should be pointed out thatupward movement of the actuating structure for the valve 39 isexperienced when the movable wheels 29 pass over a mound since the framemembers 21, 23 pivot about the pivot pin 43. This upward movement of theactuating structure of the valve 39 permits fluid under pressure tocommunicate from the source 41 to the hydraulic cylinder ram 37 whichretracts and causes the cam shaft 31 to rotate in a clockwise directionas viewed in FIG. 3 of the drawings, thus moving the wheels 29 closer tothe frame member 23, thus lowering the blade assembly 35 so it may planeoff the mound as it is caused to travel over the surface.

The linkage assembly 53 includes a pair of adjustment pins 79 which areradially disposed about the sleevelike member 73 and have one of theends thereof fixedly attached to the sleevelike member 73 in any wellknown manner as by welding or the like. Thus, this establishes free endsthereof for selective reception into the plurality of apertures 67a-67iin the vertical members 47, 59. The adjustment pins 79 are shown beingreceived in the apertures 67g in FIGS. 3 and 4 of the drawings. Itshould be understood that the pins 79 may optionally be threaded boltshaving head portions thereon which are larger than the apertures 67a-67iand the threaded shank portion extends into suitable threaded radiallydisposed apertures in the sleevelike member 73. However, I prefer thatthe pins 79 be fixedly attached to the sleevelike member 73 aspreviously described; accordingly, the respective outer ends of the pins79 are provided with transverse apertures (not shown) for receivingretainer cotter pins (not shown) so that the pins 79 may beexpeditiously attached to the bell crank assembly 45.

Still referring to FIGS. 3 and 4 of the drawings, the principalembodiment for the booster linkage 57 includes a pair of elongated rigidlink members 81 provided with suitable apertures adjacent the endsthereof for receiving a pair of pivot pins 83. The cam lever 55 also isprovided with an aperture for receiving one of the pivot pins 83 and theouter end of the horizontal arm 49 is provided with an aperture forreceiving the other pivot pin 83. It should not be obvious to thoseskilled in the art that clockwise rotation of the cam shaft 31 moves thelink members 81 upwardly, thus causing the bell crank lever assembly 45to rotate in a counterclockwise direction about the pivot pin 51 whichallows further upward travel of the actuating structure for the valve79. This additional displacement of the valve 39 causes the bladeassembly 35 to be lowered beyond the height of the mound or irregularityto slightly undercut the higher-lying areas. Ac-

cordingly, opposite actions on the linkage assembly 53 and the boosterlinkage 57 causes an opposite action on the valve 39, thus slightlyoverfilling the lower-lying areas, resulting in more perfect landleveling after natu ral settling of the fill material has occurred.

In other words, the till material compensator 11 of the presentinvention, when attached to an automatic hydro-mechanical leveler in thedescribed manner will multiply the response to any irregularity as it iscaused to travel over the surface. The multiplication factor dependsupon the particular aperture 67a-67i in which the adjustable pins 79 arereceived. The aperture 67a is adjacent the uppermost end of the arms 47,59 and exaggerates the over-compensating responsive action to thegreatest extent. Conversely, placing the pins 79 in the apertures 67ireduces the over-compensating responsive action to a minimum. Theintermediate aperture 67b-67h provide compensating action in varyingdegrees between the above-described extremes. Further, rotation of thesleeve 73 about the threaded portion of the rod 69 provides vernieradjustment of the lowest relative position of the scraper blade assemblyas governed by the roughness of the ground, the tractor horsepower,and/or the capacity of the blade 35.

Particular attention is now directed towards FIG. 5 of the drawingswherein asecond embodiment of the fill material compensator 11 of thepresent invention is shown attached to a well known horizontal andvertical articulated land plane 213. In other words, the land plane 213is similar to the land plane 13 with the main difference being that apivot pin disposed along a vertical axis enables the land leveler 213 tobe turned around or headed in an opposite direction without making awide sweeping turn. Accordingly, the leveler 213 includes anintermediate frame member 87 having the front end thereof pivotallyattached to the main frame member 21 by the pivot pin 85 and the aftendthereof pivotally attached to the tail frame member 23 by the pivot pin43. The main frame member 21 additionally includes a pair of platelikemembers 89 fixedly attached to the member 21 and extend rearwardlybeyond the member 21 at a spaced apart distance so as to overlap theintermediate member 87. The members 89 are provided with suitablyaligned apertures for receiving the pivot pin 85.

The booster linkage structure 257 for the leveler 213 includes anelongated flexible cable 91 having one end thereof attached to thehorizontal arm 49 and the other end thereof attached to the cam lever55. It should be observed that the cam lever 55 preferably is positionedradially about the cam shaft 31 at a different location than whenattached to the cam shaft 31 for the principal embodiment. In otherwords, the cam lever 55 is displaced substantially from the cam lever 55for the principal embodiment for obvious reasons.

Additionally, the booster linkage 257 for the lever 213 includes asheave structure 93 which is fixedly attached to the main frame member21 for receiving and guidingly constraining a mid-portion of the cable91, substantially as shown in FIG. 5. Additionally, a tension spring 95is included for urging rotation of the bell crank lever assembly 45 in acounterclockwise direction as viewed in FIG. 5.

More specifically, the cam shaft 31, when caused to rotate in acounterclockwise direction as viewed in FIG. 5, creates tension on thecable 91 for causing clockwise rotation of the bell crank lever assembly45. Conversely, the tension spring 95 urges the lever assembly 45 in theopposite direction when the cam shaft 31 is caused to rotate in aclockwise direction.

It should be observed that the preferred location for the apertureadjacent the outer end of the horizontal arm 49, i.e., for receiving theend of the cable 91, is along the longitudinal axis of the pivot pin 85.Further, a swivel 97 may optionally be included between the sheave 93and the arm 49 to preclude twisting of the cable 91.

The heretofore-described operation of the fill material compensator 11of the principal embodiment is also intended to describe the operationof the justdescribed alternate embodiment.

Although the invention has been described and illustrated with respectto preferred embodiments thereof, it is not to be so limited sincechanges and modifications may be made therein which are within the fullintended scope of the invention.

I claim:

1. In combination, an automatic hydro-mechanical land leveler havingarticulating frame means rigidly supported fore and aft at a fixeddistance above the ground, a pair of movable wheels supporting themidportion of said frame means at variable distances above the ground,transverse carn shaft means rotatably attached to said frame means forrotation about a first axis and rotatably supporting said pair of wheelsabout a second axis, scraper blade means depending from said frame meansfor scraping away higher laying areas of land and depositing the thuslycollected fill material into lower laying areas as said land leveler iscaused to travel over the irregular surface of the earth, hydraulic rammeans interconnecting said cam shaft and said frame means for raisingand lowering said scraper blade means by rotatably driving said camshaft about said first axis, valve means operably interposed betweensaid ram means and a source of hydraulic fluid under pressure forcontrollably actuating said ram means, a fill material compensatorapparatus comprising bell crank lever means having vertically andhorizontally disposed arms and being pivotally attached to said framemeans, first linkage means interconnecting said vertical arm of saidbell crank means and said valve means for causing said valve means to beinitially actuated when said frame means articulates as a result of saidpair of wheels rolling over a slight mound or depression thus causingsaid ram'means to rotatably drive said cam shaft about said first axisthereof to an interim position for returning said frame means to asubstantially straight line condition, cam lever means attached to saidcam shaft, and booster linkage means interconnecting said horizontal armof said bell crank means and said cam lever means for causing said rammeans to over compensate for the irregularity of the surface and furtherrotatably drive said cam shaft about said first axis beyond said interimposition thereof, thus causing said scraper blade means to slightlyundercut the higher laying areas and slightly over fill the lower layingareas as controlled by the compacted ground contact oints of the su portwheels resulting in more perfect and leveling a ter natural settling ofthe fill material has occurred.

2. The combination of claim 1 in which said vertically disposed arm ofsaid bell crank means is provided with a plurality of apertures forselectively receiving said first linkage means to adjustably control themagnitude of said over compensating responsive action of said ram means.

3. The combination of claim 1 in which said booster linkage includeselongated rigid link means interposed between said horizontally disposedarm of said bell crank means and said cam lever means, one end of saidlink means being pivotally attached to said bell crank means and theother end being pivotally attached to said cam lever means to rotatablydrive said bell crank respectively forward and backwards as said pair ofwheels roll over high and low laying areas.

4. The combination of claim 1 in which said booster linkage meansincludes elongated flexible cable means having one end thereof attachedto said horizontally disposed arm of said bell crank means and the otherend thereof attached to said cam lever means, sheave means attached tosaid frame means for receiving and guidingly constraining a mid-portionof said cable means, and spring means for urging rotation of said bellcrank means in a predetermined direction of rotation as said pair ofwheels roll over a mound and said cable means driving said bell crankmeans in an opposite direction of rotation when said pair of wheels rollover a depression in the surface of the earth.

5. The combination of claim 1 in which said booster linkage meansincludes elongated flexible cable means having one end thereof attachedto said horizontally disposed arm of said bell crank means and the otherend thereof attached to said cam levermeans, sheave means attached tosaid frame means for receiving and guidingly constraining a mid-portionof said cable means, and spring means for urging rotation of said bellcrank means in a predetermined direction of rotation as said pair ofwheels roll over a mound and said cable means driving said bell crankmeans in an opposite direction of rotation when said pair of wheels rollover a depression in the surface of the earth.

* k I! I

1. In combination, an automatic hydro-mechanical land leveler havingarticulating frame means rigidly supported fore and aft at a fixeddistance above the ground, a pair of movable wheels supporting themidportion of said frame means at variable distances above the ground,transverse cam shaft means rotatably attached to said frame means forrotation about a first axis and rotatably supporting said pair of wheelsabout a second axis, scraper blade means depending from said frame meansfor scraping away higher laying areas of land and depositing the thuslycollected fill material into lower laying areas as said land leveler iscaused to travel over the irregular surface of the earth, hydraulic rammeans interconnecting said cam shaft and said frame means for raisingand lowering said scraper blade means by rotatably driving said camshaft about said first axis, valve means operably interposed betweensaid ram means and a source of hydraulic fluid under pressure forcontrollably actuating said ram means, a fill material compensatorapparatus comprising bell crank lever means having vertically andhorizontally disposed arms and being pivotally attached to said framemeans, first linkage means interconnecting said vertical arm of saidbell crank means and said valve means for causing said valve means to beinitially actuated when said frame means articulates as a result of saidpair of wheels rolling over a slight mound or depression thus causingsaid ram means to rotatably drive said cam shaft about said first axisthereof to an interim position for returning said frame means to asubstantially straight line condition, cam lever means attached to saidcam shaft, and booster linkage means interconnecting said horizontal armof said bell crank means and said cam lever means for causing said rammeans to over compensate for the irregularity of the surface and furtherrotatably drive said cam shaft about said first axis beyond said interimposition thereof, thus causing said scraper blade means to slightlyundercut the higher laying areas and slightly over fill the lower layingareas as controlled by the compacted ground contact points of thesupport wheels resulting in more perfect land leveling after naturalsettling of the fill material has occurred.
 2. The combination of claim1 in which said vertically disposed arm of said bell crank means isprovided with a plurality of apertures for selectively receiving saidfirst linkage means to adjustably control the magnitude of said overcompensating responsive action of said ram means.
 3. The combination ofclaim 1 in which said booster linkage includes elongated rigid linkmeans interposed between said horizontally disposed arm of said bellcrank means and said cam lever means, one end of said link means beingpivotally attached to said bell crank means and the other end beingpivotally attached to said cam lever means to rotatably drive said bellcrank respectively forward and backwards as said pair of wheels rollover high and low laying areas.
 4. The combination of claim 1 in whichsaid booster linkage means includes elongated flexible cable meanshaving one end thereof attached to said horizontally disposed arm ofsaid bell crank means and the other end thereof attached to said camlever means, sheave means attached to said frame means for receiving andguidingly constraining a mid-portion of said cable means, and springmeans for urging rotation of said bell crank means in a predetermineddirection of rotation as said pair of wheels roll over a mound and saidcable means driving said bell crank means in an opposite direction ofrotation when said pair of wheels roll over a depression in the surfaceof the earth.
 5. The combination of claim 1 in which said boosterlinkage means includes elongated flexible cable means having one endthereof attached to said horizontally disposed arm of said bell crankmeans and the other end thereof attached to said cam lever means, sheavemeans attached to said frame means for receiving and guidinglyconstraining a mid-portion of said cable means, and spring means forurging rotation of said bell crank means in a predetermined direction ofrotation as said pair of wheels roll over a mound and said cable meansdriving said bell crank means in an opposite direction of rotation whensaid pair of wheels roll over a depression in the surface of the earth.